Oddly enough, by repeating the strategy Hillary supporter Ed Rendell used against Obama support Bob Casey, Jr. in the 2002 Democratic gubernatorial primary.

From Politico:

Rendell won that closely contested race with a coalition of African Americans and upscale, highly educated white voters—a coalition like the one assembled by Obama. Casey focused on blue collar workers, union households, lower-income individuals and ethnic white voters—strikingly similar to Clinton’s base in Pennsylvania.

Rendell beat Casey by winning only 10 counties out of 67 in the state. The governor won Philadelphia by 160,000 votes, and swept the four suburban counties—Bucks, Chester, Delaware and Montgomery—with 80-90 percent of the vote. He carried the Lehigh Valley, which includes Allentown, Bethlehem and Easton, by a 2-to-1 margin. He edged out Casey in Penn State’s Centre County by five points.

Casey won the other major population centers in Southwest and Central Pennsylvania, but not by enough to offset Rendell’s advantage in the populous Southeast.

To duplicate Rendell’s victory, Obama would need to show a similar level of strength as Rendell in the Philadelphia region and in the Lehigh Valley. But no polls have found him getting anywhere close.

As that last paragraph notes, it’s highly unlikely that the situation today is going to play out like this, but if it does…it’ll probably look similar.

Politics How Can Obama Win Pennsylvania?